Abstract:

To configure brake fluid a pressure controlling unit to open a high
pressure control valve to allow a high pressure generating unit that
generates a brake fluid pressure higher than the brake fluid pressure
according to brake pedal operation of a driver and a brake fluid pressure
adjusting unit that adjust the brake fluid pressure to wheel cylinders to
communicate with each other, when actual deceleration of a vehicle
becomes lower than target deceleration by execution of anti-lock brake
control during brake assist control.

Claims:

1. A vehicle braking apparatus, comprising:a brake fluid pressure
generating unit that generates a brake fluid pressure according to brake
pedal operation by a driver;a high pressure generating unit that
generates brake fluid pressure higher than the brake fluid pressure of
the brake fluid pressure generating unit;a brake fluid pressure adjusting
unit that adjusts the brake fluid pressure to be supplied to a wheel
cylinder of a wheel;a brake fluid pressure control valve that allows the
brake fluid pressure generating unit and the brake fluid pressure
adjusting unit to communicate with each other when being opened, and on
the other hand blocks the communication when being closed;a high pressure
control valve that allows the high pressure generating unit and the brake
fluid pressure adjusting unit to communicate with each other when being
opened, and on the other hand blocks the communication when being closed;
anda brake fluid pressure controlling unit that closes the brake fluid
pressure control valve at the time of brake assist control and opens the
high pressure control valve until a downstream side of the high pressure
control valve reaches a predetermined brake assist control pressure, and
controls the brake fluid pressure adjusting unit of a wheel being an
anti-lock brake control target at the time of anti-lock brake control to
increase, reduce or hold the brake fluid pressure of the wheel cylinder
of the wheel, whereinthe brake fluid pressure controlling unit is
configured to open the high pressure control valve when actual
deceleration of a vehicle becomes lower than target deceleration by
execution of the anti-lock brake control during the brake assist control.

2. The vehicle braking apparatus according to claim 1, whereinthe brake
fluid pressure controlling unit is configured to make anti-lock brake
pressure increasing control time of the brake fluid pressure adjusting
unit in the wheel being the anti-lock brake control target shorter, when
performing opening control of the high pressure control valve when
executing the anti-lock brake control during the brake assist control.

3. The vehicle braking apparatus according to claim 1, whereinthe brake
fluid pressure controlling unit is configured to gradually increase the
brake fluid pressure to be supplied to the wheel cylinder of the wheel by
controlling the brake fluid pressure adjusting unit of the wheel being
not the anti-lock brake control target, when performing opening control
of the high pressure control valve when executing the anti-lock brake
control during the brake assist control.

4. The vehicle braking apparatus according to claim 1, whereinthe brake
fluid pressure controlling unit is configured to control the high
pressure control valve based on a brake control pressure of a downstream
side of the high pressure control valve and an upstream side of the brake
fluid pressure adjusting unit at the time of normal brake assist control,
and on the other hand to open the high pressure control valve without
depending on the brake control pressure, when actual deceleration of a
vehicle becomes lower than target deceleration and the high pressure
control valve is opened during both the brake assist control and the
anti-lock brake control.

5. The vehicle braking apparatus according to claim 2, whereinthe brake
fluid pressure controlling unit is configured to gradually increase the
brake fluid pressure to be supplied to the wheel cylinder of the wheel by
controlling the brake fluid pressure adjusting unit of the wheel being
not the anti-lock brake control target, when performing opening control
of the high pressure control valve when executing the anti-lock brake
control during the brake assist control.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a vehicle braking apparatus capable
of simultaneously executing anti-lock brake control for adjusting a brake
fluid pressure to each wheel and brake assist control for supplying the
brake fluid pressure higher than a pressure of brake fluid (hereinafter,
referred to as the "brake fluid pressure") according to brake pedal
operation by a driver.

BACKGROUND ART

[0002]The vehicle braking apparatus capable of executing the brake assist
control and the anti-lock brake control is conventionally known. For
example, the vehicle braking apparatus is provided with brake fluid
pressure generating means that generates the brake fluid pressure
according to the brake pedal operation by the driver, high pressure
generating means that generates the brake fluid pressure higher than the
brake fluid pressure of the brake fluid pressure generating means and
brake fluid pressure adjusting means that adjusts the brake fluid
pressure to be supplied to a wheel cylinder of the wheel. The vehicle
braking apparatus executes the brake assist control by supplying high
brake fluid pressure of the high pressure generating means to the wheel
cylinder. Also, the vehicle braking apparatus executes the anti-lock
brake control by controlling the brake fluid pressure adjusting means to
increase, reduce or hold the brake fluid pressure of the wheel cylinder.

[0003]Meanwhile, the following Patent Document 1 discloses that the
anti-lock brake control is performed by increasing a pressure of the
wheel cylinder by the high brake fluid pressure from a high pressure
generating source during the brake assist control.

[0005]However, when the anti-lock brake control is performed during the
brake assist control by using the brake fluid pressure from the high
pressure generating source as disclosed in the above-described Patent
Document 1, a pressure increasing gradient of the brake fluid pressure of
the wheel cylinder increases and hunting occurs when increasing and
decreasing the pressure, so that controllability of the anti-lock brake
control is lowered. Therefore, there is the conventional vehicle braking
apparatus, for example, provided with a brake fluid pressure control
valve that allows the brake fluid pressure generating means and the brake
fluid pressure adjusting means to communicate with each other or blocks
the communication, and a high pressure control valve that allows the high
pressure generating means and the brake fluid pressure adjusting means to
communicate with each other or blocks the communication, that blocks the
brake fluid pressure control valve and the high pressure control valve at
the time of the anti-lock brake control during the brake assist control.

[0006]According to the conventional vehicle braking apparatus, since
pressure increasing control is not always continued by the high brake
fluid pressure from the high pressure generating means at the time of the
anti-lock brake control, lowering of the controllability of the anti-lock
brake control by the hunting as disclosed in the Patent Document 1 is
inhibited. On the other hand, in the conventional vehicle braking
apparatus, the anti-lock brake control during the brake assist control is
continued, so that an amount of the brake fluid returned to a reservoir
tank becomes large and the brake fluid pressure between the brake fluid
pressure control valve and the high pressure control valve, and the brake
fluid pressure adjusting means of each wheel is reduced. Therefore, in
the wheel, which is an anti-lock brake control target, it is possible
that the brake fluid pressure of appropriate magnitude may not be
supplied when the brake fluid pressure adjusting means performs the
pressure increasing control. Also, in the wheel, which is not the
anti-lock brake control target, it is possible that the brake fluid
pressure of the appropriate magnitude required for the brake assist
control may not be supplied due to reduction in the brake fluid pressure.
Therefore, in a vehicle at that time, actual deceleration becomes smaller
and this does not reach target deceleration, so that it is possible that
the appropriate deceleration is not performed.

[0007]Therefore, the present invention is made to improve disadvantages of
such conventional example, and an object of the present invention is to
provide the vehicle braking apparatus capable of controlling the actual
deceleration of the vehicle to the target deceleration even when the
anti-lock brake control is executed during the brake assist control.

Means for Solving Problem

[0008]In order to achieve the object, in an invention according to claim
1, a vehicle braking apparatus includes brake fluid pressure generating
means that generates a brake fluid pressure according to brake pedal
operation by a driver; high pressure generating means that generates
brake fluid pressure higher than the brake fluid pressure of the brake
fluid pressure generating means; brake fluid pressure adjusting means
that adjusts the brake fluid pressure to be supplied to a wheel cylinder
of a wheel; a brake fluid pressure control valve that allows the brake
fluid pressure generating means and the brake fluid pressure adjusting
means to communicate with each other when being opened, and on the other
hand blocks the communication when being closed; a high pressure control
valve that allows the high pressure generating means and the brake fluid
pressure adjusting means to communicate with each other when being
opened, and on the other hand blocks the communication when being closed;
and brake fluid pressure controlling means that closes the brake fluid
pressure control valve at the time of brake assist control and opens the
high pressure control valve until a downstream side of the high pressure
control valve reaches a predetermined brake assist control pressure, and
controls the brake fluid pressure adjusting means of a wheel being an
anti-lock brake control target at the time of anti-lock brake control to
increase, reduce or hold the brake fluid pressure of the wheel cylinder
of the wheel, wherein the brake fluid pressure controlling means is
configured to open the high pressure control valve when actual
deceleration of a vehicle becomes lower than target deceleration by
execution of the anti-lock brake control during the brake assist control.

[0009]Here, as in an invention in claim 2, it is preferred that the brake
fluid pressure controlling means is configured to make anti-lock brake
pressure increasing control time of the brake fluid pressure adjusting
means in the wheel being the anti-lock brake control target shorter, when
performing opening control of the high pressure control valve when
executing the anti-lock brake control during the brake assist control.

[0010]Further, as in an invention in claim 3, it is preferred that the
brake fluid pressure controlling means is configured to gradually
increase the brake fluid pressure to be supplied to the wheel cylinder of
the wheel by controlling the brake fluid pressure adjusting means of the
wheel being not the anti-lock brake control target, when performing
opening control of the high pressure control valve when executing the
anti-lock brake control during the brake assist control.

Effect of the Invention

[0011]The vehicle braking apparatus according to the present invention
supplies the high brake fluid pressure of the high pressure generating
means to an upstream part of the brake fluid pressure adjusting means,
when the actual deceleration of the vehicle becomes lower than the target
deceleration by execution of the anti-lock brake control during the brake
assist control. Therefore, the brake fluid pressure of the appropriated
magnitude according to the anti-lock brake control can be supplied to the
wheel, which is the anti-lock brake control target, and the brake fluid
pressure of the appropriate magnitude according to the brake assist
control can be supplied to the wheel, which is not the anti-lock brake
control target. Therefore, the vehicle braking apparatus can control the
actual deceleration of the vehicle at that time to the target
deceleration, thereby appropriately decelerating the vehicle.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is a view illustrating a configuration of a vehicle braking
apparatus according to the present invention.

[0013]FIG. 2 is a view illustrating an acting state of a brake fluid
pressure at the time of normal brake control of the vehicle braking
apparatus according to the present invention.

[0014]FIG. 3 is a view illustrating an example of the acting state of the
brake fluid pressure at the time of

[0015]ABS control of the vehicle braking apparatus according to the
present invention.

[0016]FIG. 4 is a view illustrating the acting state of the brake fluid
pressure at the time of brake assist control of the vehicle braking
apparatus according to the present invention.

[0017]FIG. 5 is a view illustrating an example of the acting state of the
brake fluid pressure when the ABS control is executed during the brake
assist control of the vehicle braking apparatus according to the present
invention and the view illustrating a state of a control valve STR before
actual deceleration of a vehicle becomes smaller than target
deceleration.

[0018]FIG. 6 is a view illustrating an example of the acting state of the
brake fluid pressure when the ABS control is executed during the brake
assist control of the vehicle braking apparatus according to the present
invention and the view illustrating the state of the control valve STR
when the actual deceleration of the vehicle becomes smaller than the
target deceleration.

[0019]FIG. 7 is a flowchart illustrating operation at the time of the
brake assist control of the vehicle braking apparatus according to the
present invention.

[0020]FIG. 8 is a flowchart illustrating another example of the operation
at the time of the brake assist control of the vehicle braking apparatus
according to the present invention.

EXPLANATIONS OF LETTERS OR NUMERALS

[0021]1 electronic control unit (ECU)

[0022]10 brake pedal

[0023]20 brake fluid pressure generating means

[0024]30 high pressure generating means

[0025]31 motor

[0026]32 pump

[0027]33 accumulator

[0028]40FR, 40FL, 40RR, 40RL brake fluid pressure
adjusting means

[0029]41, 42, 43, 44, 81, 82 check valve

[0030]50FR, 50FL, 50RR, 50RL wheel cylinder

[0031]91 accumulator pressure detecting sensor

[0032]92 regulator pressure detecting sensor

[0033]93 brake control pressure detecting sensor

[0034]NCFR, NCFL, NCRR, NCRL pressure reducing valve

[0035]NOFR, NOFL, NORR, NORL pressure increasing valve

[0036]SMCF control valve (pedal operational pressure control valve)

[0037]SREA control valve

[0038]SREC control valve (pedal operational pressure control valve)

[0039]STR control valve (high pressure control valve)

[0040]WFR, WFL, WRR, WRL wheel

BEST MODE(S) FOR CARRYING OUT THE INVENTION

[0041]Hereinafter, an embodiment of a vehicle braking apparatus according
to the present invention is described in detail with reference to the
drawings. Meanwhile, the present invention is not limited by the
embodiment.

Embodiment

[0042]The embodiment of the vehicle braking apparatus according to the
present invention is described with reference to FIGS. 1 to 8.

[0043]First, a configuration of the vehicle braking apparatus of the
embodiment is described with reference to FIG. 1.

[0045]The brake fluid pressure generating means 20 is provided with a
master cylinder that generates the brake fluid pressure (master cylinder
pressure Pm) according to the operational amount of the brake pedal 10 by
the driver and a hydrobooster that generates the brake fluid pressure
(regulator pressure Pr) according to the operational amount. In the
embodiment, as illustrated in FIG. 1, the brake fluid pressure generating
means 20 in which the master cylinder and the hydrobooster are integrated
with each other is illustrated as an example.

[0046]A hydrobooster unit of the brake fluid pressure generating means 20
is connected to an accumulator 33 to be described later of the high
pressure generating means 30 through brake fluid piping 61 illustrated in
FIG. 1, and this assists the operational amount (operational force) of
the brake pedal 10 at a predetermined rate by utilizing the accumulator
pressure Pa supplied from the accumulator 33 through the brake fluid
piping 61 and transmits the assisted operational amount to the master
cylinder unit. Then, the master cylinder unit generates the master
cylinder pressure Pm according to the transmitted operational amount.
Also, the hydrobooster unit generates the regulator pressure Pr
substantially as large as the master cylinder pressure Pm by input of the
master cylinder pressure Pm.

[0047]Also, the high pressure generating means 30 is provided with a motor
31, a pump 32 driven by the motor 31 to suck the brake fluid in a
reservoir tank 71 and pressurizes the same to discharge, and the
accumulator 33 that accumulates the brake fluid pressurized by the pump
32, as illustrated in FIG. 1.

[0048]The motor 31 is drive-controlled by the high pressure controlling
means of an electronic control unit (ECU) 1 illustrated in FIG. 1. The
high pressure controlling means is configured to drive the motor 31 when
the pressure in the accumulator 33 (accumulator pressure Pa) becomes
lower than a predetermined lower limit and to stop the motor 31 when the
accumulator pressure Pa becomes higher than a predetermined upper limit.
That is to say, the accumulator pressure Pa is adjusted between the lower
limit and the upper limit.

[0049]Herein, a check valve 81 that allows the brake fluid to flow from a
side of the accumulator 33 to a side of the hydrobooster unit at a
pressure not lower than a predetermined pressure and blocks the flow of
the brake fluid from the side of the hydrobooster unit to the side of the
accumulator 33 is arranged on the brake fluid piping 61 that connects the
accumulator 33 and the above-described hydrobooster unit of the brake
fluid pressure generating means 20, as illustrated in FIG. 1. The
predetermined pressure is set so as to be higher than the upper limit of
the above-described accumulator pressure Pa. Therefore, the accumulator
pressure Pa, which becomes excessively high, is not transmitted to each
of the wheel cylinders 50FR, 50FL, 50RR and 50RL, and
further a fluid pressure circuit of the high pressure generating means 30
is protected. Meanwhile, the brake fluid, which passes through the check
valve 81, is returned to the reservoir tank 71 through the hydrobooster
unit and brake fluid piping 62 illustrated in FIG. 1. Also, a pressure
sensor (hereinafter, "accumulator pressure detecting sensor") 91
illustrated in FIG. 1 that detects magnitude of the accumulator pressure
Pa is arranged on the brake fluid piping 61.

[0050]Next, the brake fluid pressure adjusting means 40FR, 40FL,
40RR and 40RL are described in detail. The brake fluid pressure
adjusting means 40FR, 40FL, 40RR and 40RL adjust the
brake fluid pressure generated by the brake fluid pressure generating
means 20 and the high pressure generating means 30 as described above,
and execute ABS control to be described later by adjusting the brake
fluid pressure to be supplied to the wheel cylinders 50FR,
50FL, 50RR and 50RL of the wheels WFR, WFL,
WRR and WRL, respectively.

[0051]The brake fluid pressure adjusting means 40FR of the right
front wheel WFR is provided with a pressure increasing valve
NOFR, which is normally opened and is closed according to a control
command of brake fluid pressure controlling means of the electronic
control unit 1, and a pressure reducing valve NCFR, which is
normally closed and is opened according to the control command of the
brake fluid pressure controlling means. In the embodiment, a two-port
two-position switching normally opened electromagnetic valve (linear
valve) is used as the pressure increasing valve NOFR, and a two-port
two-position switching normally closed electromagnetic valve (linear
valve) is used as the pressure reducing valve NCFR. The pressure
increasing valve NOFR allows an upstream part of the brake fluid
pressure adjusting means 40FR and the wheel cylinder 50FR to
communicate with each other in a nonexcited state illustrated in FIG. 1,
and on the other hand, this blocks the communication between the upstream
part of the brake fluid pressure adjusting means 40FR and the wheel
cylinder 50FR in an excited state. Also, the pressure reducing valve
NCFR blocks communication between the wheel cylinder 50FR and
the reservoir tank 71 in the nonexcited state, and on the other hand,
this allows the wheel cylinder 50FR and the reservoir tank 71 to
communicate with each other in the excited state. Meanwhile, the term
"upstream" is herein intended to mean a side of the brake fluid pressure
generating means 20 and a side of the high pressure generating means 30.
Therefore, a term "downstream" in this case is intended to mean sides of
the wheel cylinders 50FR, 50FL, 50RR and 50RL.

[0052]The brake fluid pressure adjusting means 40FR supplies the
brake fluid of the upstream part of the brake fluid pressure adjusting
means 40FR to the wheel cylinder 50FR when both of the pressure
increasing valve NOFR and the pressure reducing valve NCFR are
in the nonexcited state. According to this, the brake fluid pressure
adjusting means 40FR increases the brake fluid pressure in the wheel
cylinder 50FR of the right front wheel WFR (ABS pressure
increasing control). Also, the brake fluid pressure adjusting means
40FR holds magnitude of the brake fluid pressure in the wheel
cylinder 50FR at that time when the pressure increasing valve
NOFR is put into the excited state and the pressure reducing valve
NCFR is put into the nonexcited state (ABS holding control). Also,
the brake fluid pressure adjusting means 40FR returns the brake
fluid in the wheel cylinder 50FR to the reservoir tank 71 when both
of the pressure increasing valve NOFR and the pressure reducing
valve NCFR are in the excited state. According to this, the brake
fluid pressure adjusting means 40FR reduces the brake fluid pressure
in the wheel cylinder 50FR of the right front wheel WFR (ABS
pressure reducing control).

[0053]Further, as illustrated in FIG. 1, a check valve 41 that allows the
brake fluid to flow from the side of the wheel cylinder 50FR to
upstream of the brake fluid pressure adjusting means 40FR, and on
the other hand blocks the flow of the brake fluid from upstream of the
brake fluid pressure adjusting means 40FR to the side of the wheel
cylinder 50FR is arranged in the brake fluid pressure adjusting
means 40FR so as to be parallel to the pressure increasing valve
NOFR. The check valve 41 is arranged for rapidly reducing the brake
fluid pressure in the wheel cylinder 50FR when a control valve SMCF
to be described later is opened and the operational amount of the brake
pedal 10 is reduced such as when the driver lifts his/her foot therefrom.

[0054]The brake fluid pressure adjusting means 40FL, 40RR and
40RL of the remaining wheels WFL, WRR and WRL,
respectively, have the configuration similar to that of the
above-described brake fluid pressure adjusting means 40FR of the
right front wheel WFR as illustrated in FIG. 1. That is to say, the
brake fluid pressure adjusting means 40FL of the left front wheel
WFL is provided with a pressure increasing valve NOFL, a
pressure reducing valve NCFL and a check valve 42, and this realizes
the ABS pressure increasing control, the ABS holding control and the ABS
pressure reducing control of the brake fluid pressure of the wheel
cylinder 50FL of the left front wheel WFL, and further, rapid
reduction in the brake fluid pressure. Also, the brake fluid pressure
adjusting means 40RR of the right rear wheel WRR is provided
with a pressure increasing valve NORR, a pressure reducing valve
NCRR and a check valve 43, and this realizes the ABS pressure
increasing control, the ABS holding control and the ABS pressure reducing
control of the brake fluid pressure in the wheel cylinder 50RR of
the right rear wheel WRR, and further, rapid reduction in the brake
fluid pressure. Also, the brake fluid pressure adjusting means 40RL
of the left rear wheel WRL is provided with a pressure increasing
valve NORL, a pressure reducing valve NCRL and a check valve
44, and this realizes the ABS pressure increasing control, the ABS
holding control and the ABS pressure reducing control of the brake fluid
pressure in the wheel cylinder 50RL of the left rear wheel WRL,
and further, rapid reduction in the brake fluid pressure.

[0055]In the vehicle braking apparatus of the embodiment, the control
valve SMCF, which is normally opened and is closed according to the
control command of the brake fluid pressure controlling means of the
electronic control unit 1, is arranged between the above-described master
cylinder unit of the brake fluid pressure generating means 20 and the
upstream parts of the brake fluid pressure adjusting means 40FR and
40FL of the front wheels WFR and WFL, respectively.

[0056]In the embodiment, the two-port two-position switching normally
opened electromagnetic valve is used as the control valve SMCF. The
control valve SMCF is opened in the nonexcited state illustrated in FIG.
1 to allow the master cylinder unit and the upstream parts of the brake
fluid pressure adjusting means 40FR and 40FL of the front
wheels WFR and WFL, respectively, to communicate with each
other, and on the other hand, this is closed in the excited state
illustrated in FIG. 3, for example, to block the communication between
the master cylinder unit and the upstream parts of the brake fluid
pressure adjusting means 40FR and 40FL of the front wheels
WFR and WFL, respectively. Therefore, the master cylinder
pressure Pm is supplied from the master cylinder unit of the brake fluid
pressure generating means 20 to an upstream part of the control valve
SMCF. That is to say, the control valve SMCF serves as a brake fluid
pressure control valve that executes or stops the supply of the master
cylinder pressure Pm to the upstream parts of the brake fluid pressure
adjusting means 40FR and 40FL.

[0057]Also, in the vehicle braking apparatus, a control valve SREC, which
is normally opened and is closed according to the control command of the
brake fluid pressure controlling means of the electronic control unit 1,
is arranged between the above-described hydrobooster unit of the brake
fluid pressure generating means 20 and an upstream parts of the brake
fluid pressure adjusting means 40RR and 40RL of the rear wheels
WRR and WRL, respectively. In the embodiment, the two-port
two-position switching normally opened electromagnetic valve (linear
valve) is used as the control valve SREC. The control valve SREC is
opened in the nonexcited state illustrated in FIG. 1 to allow the
hydrobooster unit and the upstream parts of the brake fluid pressure
adjusting means 40RR and 40RL of the rear wheels WRR and
WRL, respectively, to communicate with each other, and on the other
hand, this is closed in the excited state illustrated in FIG. 4, for
example, to block the communication between the hydrobooster unit and the
upstream parts of the brake fluid pressure adjusting means 40RR and
40RL of the rear wheels WRR and WRL, respectively.
Therefore, the regulator pressure Pr is supplied from the hydrobooster
unit of the brake fluid pressure generating means 20 to an upstream part
of the control valve SREC. That is to say, the control valve SREC serves
as the brake fluid pressure control valve that executes or stops the
supply of the regulator pressure Pr to the upstream parts of the brake
fluid pressure adjusting means 40RR and 40RL. In the vehicle
braking apparatus of the embodiment, a pressure sensor (hereinafter,
referred to as a "regulator pressure detecting sensor") 92 illustrated in
FIG. 1 that detects magnitude of the regulator pressure Pr is arranged in
the upstream part of the control valve SREC.

[0058]Herein, a check valve 82 is arranged in the vehicle braking
apparatus so as to be parallel to the control valve SREC. The check valve
82 allows the brake fluid to flow from upstream to downstream of the
control valve SREC, and on the other hand, this blocks the flow of the
brake fluid from downstream to upstream thereof. The check valve 82 can
increase the brake fluid pressure in the wheel cylinders 50RR and
50RL of the rear wheels WRR and WRL, respectively, by
operating when the control valve SREC is in the excited state (closed
state) and the driver increases the operational amount of the brake pedal
10. At that time, when a control valve SREA illustrated in FIG. 1 to be
described later is opened, the check valve 82 can also increase the brake
fluid pressure in the wheel cylinders 50FR and 50FL of the
front wheels WFR and WFL, respectively, by the increase of the
operational amount of the brake pedal 10.

[0059]Further, brake fluid piping 63 that connects a downstream part of
the above-described control valve SMCF (in other words, the upstream
parts of the brake fluid pressure adjusting means 40FR and 40FL
of the front wheels WFR and WFL, respectively), a downstream
part of the control valve SREC (in other words, the upstream parts of the
brake fluid pressure adjusting means 40RR and 40RL of the rear
wheels WRR and WRL, respectively), and a downstream part of a
control valve STR to be described later (in other words, the upstream
parts of the brake fluid pressure adjusting means 40RR and 40RL
of the rear wheels WRR and WRL, respectively) is arranged in
the vehicle braking apparatus. Then, the control valve SREA, which is
normally closed and is opened according to the control command of the
brake fluid pressure controlling means of the electronic control unit 1,
is arranged between the downstream parts of the control valve SMCF and
the control valve SREC on the brake fluid piping 63. In the embodiment,
the two-port two-position switching normally closed electromagnetic valve
is used as the control valve SREA. The control valve SREA is closed in
the nonexcited state illustrated in FIG. 1 to block communication between
the downstream part of the control valve SMCF (upstream parts of the
brake fluid pressure adjusting means 40FR and 40FL of the front
wheels WFR and WFL, respectively) and the downstream part of
the control valve

[0060]SREC (upstream parts of the brake fluid pressure adjusting means
40RR and 40RL of the rear wheel WRR and WRL,
respectively), and on the other hand, this is opened in the excited state
illustrated in FIG. 3, for example, to allow them to communicate with
each other. Meanwhile, the downstream part of the control valve SREC and
the downstream part of the control valve STR are always in communication
with each other through the brake fluid piping 63.

[0061]Also, the vehicle braking apparatus is provided with the control
valve STR, which is normally closed and is opened according to the
control command of the brake fluid pressure controlling means of the
electronic control unit 1, between the above-described high pressure
generating means 30 (specifically, the brake fluid piping 61) and the
brake fluid piping 63. In the embodiment, the two-port two-position
switching normally closed electromagnetic valve (linear valve) is used as
the control valve STR. The control valve STR is closed in the nonexcited
state illustrated in FIG. 1 to block communication between the high
pressure generating means 30 and the brake fluid piping 63, and on the
other hand, this is opened in the excited state illustrated in FIG. 6,
for example, to allow the high pressure generating means 30 and the brake
fluid piping 63 to communicate with each other. Therefore, the
accumulator pressure Pa is supplied from the high pressure generating
means 30 to the upstream part of the control valve STR, and the control
valve STR serves as a high pressure control valve for supplying a brake
assist control pressure PcBA at the time of brake assist control to
be described later to the wheel cylinders 50FR, 50FL, 50RR
and 50RL of the wheels WFR, WFL, WRR and WRL,
respectively. In the vehicle braking apparatus of the embodiment, a
pressure sensor (hereinafter, referred to as a "brake control pressure
detecting sensor") 93 illustrated in FIG. 1 that detects magnitude of a
brake fluid pressure Pc (hereinafter, referred to as a "brake control
pressure") of the brake fluid piping 63 is arranged.

[0062]In the vehicle braking apparatus of the embodiment configured as
described above, the brake fluid pressure controlling means controls all
of the control valves SMCF, SREA, SREC and STR in the nonexcited state
when performing normal brake control illustrated in FIG. 2. Also, at that
time, the brake fluid pressure controlling means controls all of the
pressure increasing valves NOFR, NOFL, NORR and NORL
and the pressure reducing valves NCFR, NCFL, NCRR and
NCRL of the brake fluid pressure adjusting means 40FR,
40FL, 40RR and 40RL of the wheels WFR, WFL,
WRR and WRL, respectively, in the nonexcited state.

[0063]According to this, the control valve SMCF is opened and the control
valve SREA is closed, so that the master cylinder pressure Pm is supplied
to each of the upstream parts of the brake fluid pressure adjusting means
40FR and 40FL of the front wheels WFR and WFL,
respectively. Then, since the brake fluid pressure adjusting means
40FR and 40FL of the front wheels WFR and WFL at that
time are in the above-described ABS pressure increasing control state,
the master cylinder pressure Pm is supplied to each of the wheel
cylinders 50FR and 50FL of the front wheels WFR and
WFL, respectively. On the other hand, since the control valve SREC
is opened and the control valve STR is closed at that time, the regulator
pressure Pr is supplied to each of the upstream parts of the brake fluid
pressure adjusting means 40RR and 40RL of the rear wheels
WRR and WRL, respectively. Then, since the brake fluid pressure
adjusting means 40RR and 40RL of the rear wheels WRR and
WRL at that time are in the ABS pressure increasing control state,
the regulator pressure Pr is supplied to each of the wheel cylinders
50RR and 50RL of the rear wheels WRR and WRL,
respectively. That is to say, the master cylinder pressure Pm and the
regulator pressure Pr according to the operational amount of the brake
pedal 10 by the driver are supplied to the front wheels WFR and
WFL, and the rear wheels WRR and WRL, respectively, at the
time of the normal brake control, and the braking force according to the
master cylinder pressure Pm and the regulator pressure Pr act on the
front wheels WFR and WFL and the rear wheels WRR and
WRL. Meanwhile, the brake control pressure detecting sensor 93 at
the time of the normal brake control detects the regulator pressure Pr as
the brake control pressure Pc.

[0064]Also, when performing anti-lock brake control (ABS control), the
brake fluid pressure controlling means controls the control valves SMCF
and SREA in the excited state and controls the control valves SREC and
STR in the nonexcited state, as illustrated in FIG. 3. At that time, the
brake fluid pressure controlling means allows the brake fluid pressure
adjusting means 40FR or 40FL or 40RR or 40RL, which
is an ABS control target, to switch the ABS pressure increasing control,
the ABS pressure reducing control and the ABS holding control according
to a slip ratio and the like of the wheels WFR, WFL, WRR
and WRL.

[0065]According to this, the control valve SMCF is closed, so that the
supply of the master cylinder pressure Pm from the master cylinder unit
of the brake fluid pressure generating means 20 to the upstream parts of
the brake fluid pressure adjusting means 40FR and 40FL of the
front wheels WFR and WFL, respectively, is blocked. On the
other hand, the control valve SREC is opened and the control valve STR is
closed as at the time of the normal brake control, so that the regulator
pressure Pr is supplied to each of the upstream parts of the brake fluid
pressure adjusting means 40RR and 40RL of the rear wheels
WRR and WRL, respectively. Since the control valve SREA is
opened at that time, the regulator pressure Pr is supplied to each of the
upstream parts of the brake fluid pressure adjusting means 40FR and
40FL of the front wheels WFR and WFL, respectively.
Therefore, the brake fluid pressure obtained by adjusting the regulator
pressure Pr by the brake fluid pressure adjusting means 40FR,
40FL, 40RR and 40RL according to the slip ratio and the
like is supplied to the wheel cylinders 50FR, 50FL, 50RR
and 50RL of the wheels WFR, WFL, WRR and WRL,
respectively. Meanwhile, the brake control pressure detecting sensor 93
at the time of the ABS control detects the regulator pressure Pr as the
brake control pressure Pc.

[0066]Also, when performing the brake assist control (BA control), the
brake fluid pressure controlling means is allowed to control the control
valves SMCF, SREA, SREC, STR and the like to increase the brake control
pressure Pc of the brake fluid piping 63 to be "regulator pressure
Pr+additional amount of the brake fluid pressure required for the brake
assist control" and to supply the brake control pressure (hereinafter,
referred to as the "brake assist control pressure") PcBA required
for the brake assist control to the wheel cylinders 50FR, 50FL,
50RR and 50RL of the wheels WFR, WFL, WRR and
WRL, respectively. Specifically, the brake fluid pressure
controlling means at that time controls the control valves SMCF and SREA
in the excited state as illustrated in FIG. 4 and further switches the
control valves STR and SREC between the nonexcited state and the excited
state according to the brake assist control pressure PcBA. Further,
at that time, the brake fluid pressure controlling means controls the
pressure increasing valves NOFR, NOFL, NORR and NORL
and the pressure reducing valves NCFR, NCFL, NCRR and
NCRL of the brake fluid pressure adjusting means 40FR,
40FL, 40RR and 40RL of the wheels WFR, WFL,
WRR and WRL, respectively, in the nonexcited state. That is to
say, in the vehicle braking apparatus, the brake assist control pressure
PcBA is adjusted by switching opening and closing of the control
valves STR and SREC as the brake assist pressure control valves, thereby
executing the brake assist control. Meanwhile, the brake assist control
pressure PcBA and the additional amount of the brake fluid pressure
required for the brake assist control are determined according to the
operational amount (pedal force and the like) of the brake pedal 10 by
the driver, the regulator pressure Pr, a vehicle speed and the like, for
example.

[0067]For example, when performing the brake assist control, the brake
fluid pressure controlling means observes pressure difference between
detected values of the regulator pressure detecting sensor 92 and the
brake control pressure detecting sensor 93 and switches the control
valves STR and SREC between the excited state (opened state) and the
nonexcited state (closed state) such that the pressure difference becomes
the accumulator pressure Pa. According to this, the accumulator pressure
Pa of the high pressure generating means 30 is supplied to the brake
fluid piping 63 with the regulator pressure Pr, so that the brake assist
control pressure PcBA (=regulator pressure Pr+accumulator pressure
Pa) is supplied to the wheel cylinders 50FR, 50FL, 50RR
and 50RL of the wheels WFR, WFL, WRR and WRL,
respectively. After the brake assist control pressure PcBA is
detected by the brake control pressure detecting sensor 93, the brake
fluid pressure controlling means controls the control valve STR into the
nonexcited state (closed state) illustrated in FIG. 4 to hold the brake
fluid pressure of each of the wheel cylinders 50FR, 50FL,
50RR and 50RL at the brake control pressure Pc required for the
brake assist control.

[0068]Herein, there is a case in which the ABS control is executed during
execution of the brake assist control. In this case, the brake fluid
pressure controlling means switches the control valves SREC and STR
between the nonexcited state and the excited state same as when
performing the brake assist control alone, thereby generating the brake
assist control pressure PcPA in the brake fluid piping 63. Also, the
brake fluid pressure controlling means at that time switches the pressure
increasing valve NOFR or NOFL or NORR or NORL and the
pressure reducing valve NCFR or NCFL or NCRR or NCRL
of the brake fluid pressure adjusting means 40FR or 40FL or
40RR or 40RL, which is the ABS control target, among the ABS
pressure increasing control state, the ABS pressure reducing control
state and the ABS holding control state, same as when performing the ABS
control alone, thereby preventing the wheel WFR or WFL or
WRR or WRL, which is the ABS control target, from being locked.

[0069]When the control valves SMCF, SREC and STR are closed and the
control valve SREA is opened in association with the execution of the
brake assist control alone as illustrated in FIG. 4, the brake fluid
between the downstream parts of the control valves SMCF, SREC and STR and
the wheel cylinders 50FR, 50FL, 50RR and 50RL holds
the high brake assist control pressure PcBA and has nowhere to go.
Therefore, between them, only slight change in brake fluid amount largely
changes the brake fluid pressure.

[0070]When the ABS control is started under such a circumstance, the brake
fluid pressure adjusting means 40FR or 40FL or 40RR or
40RL, which is the ABS control target, is allowed to perform the ABS
pressure reducing control, so that the pressure increasing valve
NOFR or NOFL or NORR or NORL, which is the ABS
control target, is closed, and at the same time, the pressure reducing
valve NCFR or NCFL or NCRR or NCRL is opened, and a
part of the brake fluid between a downstream part of the pressure
increasing valve NOFR or NOFL or NORR or NORL, which
is the ABS control targets, and the wheel cylinder 50FR or 50FL
or 50RR or 50RL, which is the ABS control target, is returned
to the reservoir tank 71. Therefore, the brake fluid pressure is reduced
between the downstream part of the pressure increasing valve NOFR or
NOFL or NORR or NORL, which is the ABS control target, and
the wheel cylinder 50FR or 50FL or 50RR and 50RL,
which is the ABS control target.

[0071]Then, in the ABS control after that, when the brake fluid pressure
adjusting means 40FR or 40FL or 40RR or 40RL, which
is the ABS control target, is allowed to perform the ABS pressure
increasing control, the pressure increasing valve NOFR or NOFL
or NORR or NORL, which is the ABS control target, is opened,
and at the same time the pressure reducing valve NCFR or NCFL
or NCRR or NCRL is closed. At that time, a part of the brake
fluid between the upstream parts of the pressure increasing valves
NOFR, NOFL, NORR and NORL and the control valves
SMCF, SREC and STR flows between the downstream part of the pressure
increasing valve NOFR or NOFL or NORR or NORL, which
is the ABS control target, and the wheel cylinder 50FR or 50FL
or 50RR or 50RL, which is the ABS control target. Therefore,
the brake control pressure Pc (<brake assist control pressure
PcBA) is reduced between the upstream parts of the pressure
increasing valves NOFR, NOFL, NORR and NORL and the
control valves SMCF, SREC and STR (that is to say, in the brake fluid
piping 63).

[0072]When the ABS control is executed during the brake assist control in
this manner, the brake control pressure Pc of the brake fluid piping 63
is largely reduced while the brake fluid pressure adjusting means
40FR or 40FL, or 40RR or 40RL, which is the ABS
control target, alternately repeats the ABS pressure increasing control,
the ABS pressure reducing control and the ABS holding control. Therefore,
at that time, since the brake control pressure Pc of the brake fluid
piping 63 is deficient, it is possible that the brake fluid pressure of
appropriate magnitude required for the ABS pressure increasing control
may not be supplied to the wheel cylinder 50FR or 50FL or
50RR or 50RL, which is the ABS control target, even when the
brake fluid pressure adjusting means 40FR or 40FL or 40RR
or 40RL, which is the ABS control target, is switched from the ABS
pressure reducing control and the ABS holding control to the ABS pressure
increasing control. According to this, in a vehicle, actual deceleration
(hereinafter, referred to as "actual deceleration") becomes smaller and
this does not reach target deceleration, so that it is possible that
appropriate deceleration is not performed. Further, since the brake fluid
pressure adjusting means 40FR or 40FL or 40RR or
40RL, which is not the ABS control target, is in the ABS pressure
increasing control state (that is to say, the pressure increasing valve
NOFR or NOFL or NORR or NORL thereof is opened), it
is possible that the brake fluid pressure of the appropriate magnitude
required for the brake assist control may not be supplied in association
with deficiency of the brake control pressure Pc in the brake fluid
piping 63 also to the wheel cylinder 50FR or 50FL or 50RR
or 50RL, which is not the ABS control target, at that time.
Therefore, in the vehicle at that time, the actual deceleration becomes
further smaller and this does not reach the target deceleration, so that
it is highly possible that the appropriate deceleration is not performed.

[0073]Then, the vehicle braking apparatus of the embodiment is configured
to be able to control the actual deceleration of the vehicle to the
target deceleration even when the ABS control is executed during the
brake assist control.

[0074]Specifically, in the embodiment, the brake fluid pressure
controlling means is configured to put the control valve STR in the
closed state in FIG. 5 into the excited state to open as illustrated in
FIG. 6 when the actual deceleration of the vehicle becomes smaller than
the target deceleration when the ABS control is executed during the brake
assist control. That is to say, in the embodiment, the accumulator
pressure Pa is supplied to the brake fluid piping 63 to increase the
pressure by opening the control valve STR in such a case, and the brake
fluid pressure appropriate for the ABS control is supplied to the wheel
cylinder 50FR or 50FL or 50RR, or 50RL, which is the
ABS control target, and on the other hand, the brake fluid pressure
appropriate for the brake assist control is supplied to the wheel
cylinder 50FR or 50FL or 50RR or 50RL, which is not
the ABS control target.

[0075]Herein, the accumulator pressure Pa is adjusted so as to be the
additional amount of the brake fluid pressure required for the brake
assist control, as described above. Therefore, the brake fluid pressure
(brake assist control pressure PcBA) of the appropriate magnitude is
supplied to the wheel cylinder 50FR or 50FL or 50RR or
50RL, which is not the ABS control target, by the accumulator
pressure Pa supplied to the brake fluid piping 63. On the other hand, in
the wheel cylinder 50FR or 50FL or 50RR or 50RL,
which is the ABS control target, although the brake fluid pressure can be
rapidly increased during the ABS pressure increasing control by the
accumulator pressure Pa supplied to the brake fluid piping 63, if
execution time of the ABS pressure increasing control (hereinafter,
referred to as "ABS pressure increasing control time") is not suitable,
deficiency or excess occurs in the brake fluid pressure. In the
embodiment, since the brake control pressure Pc of the brake fluid piping
63 is of the same magnitude (brake assist control pressure PcBA) as
that before the start of the ABS control by the supply of the accumulator
pressure Pa, if the ABS pressure increasing control time is the same as
that before the supply of the accumulator pressure Pa, excessive brake
fluid pressure (brake assist control pressure PcBA at the maximum)
is supplied to the wheel cylinder 50FR or 50FL or 50RR or
50RL, which is the ABS control target. Therefore, it is possible
that the wheel WFR or WFL or WRR or WRL, which is the
ABS control target, is locked even during the ABS control by the
excessive brake fluid pressure. Therefore, in the embodiment, the brake
fluid pressure controlling means is configured such that the ABS pressure
increasing control time is shorter than that before the supply of the
accumulator pressure Pa in order to prevent the wheel WFR or
WFL or WRR or WRL, which is the ABS control target, from
being locked in association with the supply of the accumulator pressure
Pa.

[0076]Hereinafter, operation at the time of the brake assist control of
the vehicle braking apparatus of the embodiment is described with
reference a flowchart in FIG. 7.

[0077]First, the brake fluid pressure controlling means of the embodiment
judges whether it is currently in the brake assist control (BA control)
based on contents of the control command thereof for the control valves
SMCF, SREA, SREC, STR and the like, for example (step ST1).

[0078]When the brake fluid pressure controlling means judges that it is
not in the brake assist control, this finishes a calculation process once
and repeats the judgment at the step ST1.

[0079]On the other hand, when it is judged to be in the brake assist
control at the above-described step ST1, the brake fluid pressure
controlling means calculates the target deceleration of the vehicle at
that time (step ST2). For example, at the step ST2, the target
deceleration is obtained based on map data and the like in which the
operational amount of the brake pedal 10 by the driver or the regulator
pressure Pr detected by the regulator pressure detecting sensor 92
(≈master cylinder pressure Pm) and the brake assist control
pressure PcBA as a control target value or the accumulator pressure
Pa detected by the accumulator pressure detecting sensor 91 (=additional
amount of the brake fluid pressure required for the brake assist control)
are used as parameters.

[0080]Subsequently, the brake fluid pressure controlling means observes
whether the contents of the control command for each of the brake fluid
pressure adjusting means 40FR, 40FL, 40RR and 40RL
are about the ABS pressure increasing control, the ABS pressure reducing
control and the like to judge whether any one of the wheels WFR,
WFL, WRR and WRL is the ABS control target (that is to
say, whether it is in the ABS control) (step ST3).

[0081]When it is judged to be in the ABS control at the step ST3, the
brake fluid pressure controlling means compares the actual deceleration
of the vehicle obtained based on a detected value (vehicle front-rear
acceleration) of a vehicle front-rear acceleration sensor 101 illustrated
in FIG. 1, for example, and the target deceleration at the
above-described step ST2 to judge whether the actual deceleration becomes
smaller than the target deceleration (step ST4).

[0082]When it is judged that the actual deceleration is smaller than the
target deceleration at the step ST4, the brake fluid pressure controlling
means puts the control valve STR in the nonexcited state (closed state)
into the excited state to open the same (step ST5).

[0083]In association with the valve opening, the accumulator pressure Pa
of the high pressure generating means 30 is supplied to the brake fluid
piping 63, so that the brake fluid pressure of the wheel cylinder
50FR or 50FL or 50RR or 50RL of the wheel WFR or
WFL or WRR or WRL, which is not the ABS control target, is
increased to that of the appropriate magnitude (brake assist control
pressure PcBA) at the same time as the opening of the control valve
STR.

[0084]On the other hand, when the brake fluid pressure adjusting means
40FR or 40FL or 40RR or 40RL of the wheel WFR or
WFL or WRR or WRL, which is the ABS control target, is put
into the ABS pressure increasing control state after the opening of the
control valve STR, the brake fluid pressure of the wheel cylinder
50FR or 50FL or 50RR or 50RL of the wheel WFR or
WFL or WRR or WRL, which is the ABS control target, can be
rapidly increased by the high accumulator pressure Pa supplied to the
brake fluid piping 63. Therefore, the appropriate ABS control can be
executed to the wheel WFR or WFL or WRR or WRL, which
is the ABS control target.

[0085]Herein, when the ABS pressure increasing control is performed to the
wheel cylinder 50FR or 50FL or 50RR or 50RL, which is
the ABS control target, by the brake fluid pressure adjusting means
40FR or 40FL or 40RR or 40RL, which is the ABS
control target, with the ABS pressure increasing control time (anti-lock
brake pressure increasing control time) as long as that so far while
supplying the brake fluid pressure in the brake fluid piping 63, which is
the accumulator pressure Pa at the maximum, the excessive brake fluid
pressure is supplied to the wheel cylinder 50FR or 50FL or
50RR or 50RL, as described above. Therefore, the brake fluid
pressure controlling means sets the ABS pressure increasing control time,
which prevents the wheel WFR or WFL or WRR or WRL,
which is the ABS control target, from being locked by the excessive brake
fluid pressure according to the accumulator pressure Pa, the slip ratio
and the like of the wheel WFR or WFL or WRR or WRL,
which is the ABS control target. That is to say, the brake fluid pressure
controlling means corrects the ABS pressure increasing control time to be
shorter than that before the control valve STR is opened at the
above-described step ST5 (step ST6). According to this, in the wheel
WFR or WFL or WRR or WRL, which is the ABS control
targets, the supply of the excessive brake fluid pressure can be
prevented while the deficiency of the brake fluid pressure for the wheel
cylinder 50FR or 50FL or 50RR or 50RL thereof is
immediately compensated.

[0086]Herein, when it is judged not to be in the ABS control at the
above-described step ST3, the brake fluid pressure controlling means
performs closing control of the control valve STR (step ST7). At the step
ST7, when the control valve STR is already closed, this is kept in the
closed state (nonexcited state). On the other hand, when the control
valve STR is kept opening just after the start of the brake assist
control, for example, the opened state (excited state) is switched to the
closed state (nonexcited state) and the execution of the brake assist
control is continued. Also, when the control valve STR is opened through
the above-described step ST5, for example, the opened state (excited
state) is switched to the closed state (nonexcited state) and it returns
to the brake assist control alone.

[0087]Also, when it is judged that the actual deceleration is not smaller
than the target deceleration at the above-described step ST4, the brake
fluid pressure controlling means shifts to the above-described step ST7
to perform the closing control of the control valve STR. At the step ST7
at that time, combination of the brake assist control and the ABS control
is continued regardless of whether the control valve STR is closed or
opened.

[0088]The brake fluid pressure controlling means of the embodiment repeats
the above-described calculation process as long as it is in the brake
assist control. According to this, when the ABS control is executed
during the brake assist control, the vehicle braking apparatus of the
embodiment can supply the brake fluid pressure according to the ABS
control to the wheel cylinders 50FR, 50FL, 50RR and
50RL of the wheels WFR, WFL, WRR and WRL, in the
ABS control, respectively, without deficiency or excess and with high
responsibility. Also, this can continue supplying the appropriate brake
fluid pressure according to the brake assist control to the wheel
cylinders 50FR, 50FL, 50RR and 50RL of the wheels
WFR, WFL, WRR and WRL, respectively, which are not in
the ABS control. Therefore, the vehicle braking apparatus of the
embodiment can prevent the actual deceleration of the vehicle from being
lower than the target deceleration even when the ABS control is executed
during the brake assist control and can control the actual deceleration
to the target deceleration, thereby appropriately decelerating the
vehicle.

[0089]The ABS control is principally executed at the time of moving to a
road surface of which friction coefficient is low (low μ road). In
this case, in general, the front wheels WFR and WFL first move
to the low μ road and thereafter the rear wheels WRR and WRL
move to the low μ road. Therefore, at the start of the ABS control,
there is a situation in which the rear wheels WRR and WRL are
not in the ABS control state even when the front wheels WFR and
WFL are in the ABS control. Herein, from a viewpoint of
stabilization of behavior of the vehicle, for example, rapid change in
braking force and driving force of the rear wheels WRR and WRL
are not preferable. However, when only the front wheels WFR and
WFL are in the ABS control during the brake assist control, the
pressure increasing valves NORR and NORL of the rear wheels
WRR and WRL, respectively, are opened, so that it is possible
that the braking force of the rear wheels WRR and WRL before
the start of the ABS control rapidly increases by the supply of the
above-described accumulator pressure Pa to the brake fluid piping 63. For
example, when the brake control pressure Pc of the brake fluid piping 63
becomes significantly lower than the brake assist control pressure
PcBA and then the actual deceleration of the vehicle becomes lower
than the target deceleration, the brake control pressure Pc of the brake
fluid piping 63 significantly and rapidly increases up to the brake
assist control pressure PcBA by the supply of the accumulator
pressure Pa, so that the braking force of the rear wheels WRR and
WRL before the start of the ABS control rapidly increase. Meanwhile,
as for the pressure increasing valves NOFR and NOFL of the
front wheels WFR and WFL during the ABS control, respectively,
are basically closed and are opened when executing the ABS pressure
increasing control, so that the possibility that the braking force of the
front wheels WFR and WFL rapidly increases is low.

[0090]Then, the vehicle braking apparatus of the embodiment is configured
to gradually increase the brake fluid pressure of the wheel cylinders
50RR and 50RL of the rear wheels WRR and WRL before
the start of the ABS control, respectively, in such a case so as not to
rapidly change the braking force of the rear wheels WRR and
WRL. Specifically, the brake fluid pressure controlling means is
configured such that the brake fluid pressure of the wheel cylinders
50RR and 50RL gradually increases by repeatedly opening and
closing the pressure increasing valves NORR and NORL of the
rear wheels WRR and WRL, respectively, which are opened in the
brake assist control, if the ABS control of the rear wheels WRR and
WRL is not started yet.

[0091]Hereinafter, operation at the time of the brake assist control of
the vehicle braking apparatus in this case is described with reference to
a flowchart in FIG. 8.

[0092]First, the brake fluid pressure controlling means judges whether it
is in the brake assist control (BA control) as at the above-described
step ST1 (step ST11), and when it is in the brake assist control, this
calculates the target deceleration of the vehicle as at the
above-described step ST2 (step ST12). Meanwhile, when it is judged not to
be in the brake assist control at the step ST11, this finishes the
calculation process once and repeats the judgment at the step ST11 again.

[0093]Subsequently, the brake fluid pressure controlling means observes
whether the contents of the control command for the brake fluid pressure
adjusting means 40FR and 40FL of the front wheels WFR and
WFL, respectively, are about the ABS pressure increasing control,
the ABS pressure reducing control and the like, for example, and judges
whether both of the front wheels WFR and WFL are in the ABS
control (step ST13).

[0094]When it is judged that both of the front wheels WFR and
WFL are in the ABS control at the step ST13, the brake fluid
pressure controlling means compares the actual deceleration of the
vehicle and the target deceleration at the above-described step ST12 to
judges whether the actual deceleration is smaller than the target
deceleration as at the above-described step ST4 (step ST14).

[0095]When it is judged that the actual deceleration is smaller than the
target deceleration at the step ST14, the brake fluid pressure
controlling means puts the control valve STR in the nonexcited state
(closed state) into the excited state to open the same (step ST15). Then,
the brake fluid pressure controlling means corrects the ABS pressure
increasing control time so as to be shorter than that before the control
valve STR is opened at the above-described step ST15 as at the
above-described step ST6 (step ST16).

[0096]According to this, in the front wheels WFR and WFL, which
are the ABS control targets, the deficiency of the brake fluid pressure
for the wheel cylinders 50FR and 50FL of the front wheels
WFR and WFL, respectively, is immediately compensated by the
brake control pressure Pc of the brake fluid piping 63 increased by the
supply of the accumulator pressure Pa in association with the opening of
the control valve STR, as in the above-described illustration, and the
appropriate ABS control is executed. Also, at that time, the ABS pressure
increasing control time is made appropriate, so that the supply of the
excessive brake fluid pressure to the wheel cylinders 50FR and
50FL can be prevented.

[0097]Further, the brake fluid pressure controlling means observes whether
the contents of the control command for the brake fluid pressure
adjusting means 40RR and 40RL of the rear wheels WRR and
WRL, respectively, are about the ABS pressure increasing control,
the ABS pressure reducing control and the like to judge whether the ABS
control of the rear wheels WRR and WRL is started (that is to
say, whether they are in an ABS non-control state) (step ST18).

[0098]When it is judged that the ABS control of the rear wheels WRR
and WRL is not started yet (that is to say, in the ABS non-control
state) at the step ST18, the brake fluid pressure controlling means
gradually increases the brake fluid pressure of the wheel cylinders
50RR and 50RL of the rear wheels WRR and WRL,
respectively (step ST19). At the step ST19, the pressure increasing
valves NORR and NORL of the rear wheel WRR and WRL,
respectively, which are opened, are closed and opened again, and the
opening and closing are repeated, for example.

[0099]According to this, in the rear wheels WRR and WRL before
the start of the ABS control, the brake fluid pressure of the wheel
cylinders 50RR and 50RL is gradually increased up to the brake
assist control pressure PcBA. Therefore, in the rear wheels WRR
and WRL, rapid increase in the braking force when the high
accumulator pressure Pa is supplied in association with the opening of
the control valve STR can be prevented. Therefore, herein, the behavior
of the vehicle at that time can be kept in a stable state.

[0100]Herein, when it is judged that both of the front wheels WFR and
WFL are not in the ABS control at the above-described step ST13, and
also when it is judged that the actual deceleration is not smaller than
the target deceleration at the above-described step ST14, the brake fluid
pressure controlling means performs the closing control of the control
valve STR according to each case as at the above-described step ST7 (step
ST17).

[0101]Also, when it is judged that the rear wheels WRR and WRL
are in the ABS control at the above-described step ST18, the brake fluid
pressure controlling means finishes the calculation process once and
returns to the above-described step ST11.

[0102]As described above, the vehicle braking apparatus of the embodiment
can control the actual deceleration of the vehicle to the target
deceleration while keeping the behavior of the vehicle stable by
gradually increasing the brake fluid pressure supplied to the rear wheels
WRR and WRL before the start of the ABS control, when the ABS
control is executed during the brake assist control and the actual
deceleration of the vehicle is likely to be lower than the target
deceleration.

[0103]Herein, in the viewpoint of the stabilization of the behavior of the
vehicle, it is desirable the most to gradually increase the brake fluid
pressure of the rear wheels WRR and WRL before the start of the
ABS control or which are not the ABS control targets. However, even when
the targets of the increase of the brake fluid pressure are the front
wheels WFR and WFL, which are not in the ABS control, they
dedicate to the stabilization of the behavior of the vehicle. Therefore,
it is preferable that the vehicle braking apparatus of the embodiment is
configured to gradually increase the brake fluid pressure supplied to the
wheel WFR or WFL or WRR or WRL, which is not the ABS
control target, without regard to the front wheels WFR and WFL
and the rear wheels WRR and WRL when the ABS control is
executed during the brake assist control and the actual deceleration of
the vehicle is likely to be lower than the target deceleration.

INDUSTRIAL APPLICABILITY

[0104]As described above, the vehicle braking apparatus according to the
preset invention is applicable to technology to control the actual
deceleration of the vehicle to the target deceleration when the ABS
control is executed during the brake assist control.